Molecular sieves are a commercially important class of crystalline materials. They have distinct crystal structures with ordered pore structures which are demonstrated by distinct X-ray diffraction patterns. The crystal structure defines cavities and pores which are characteristic of the different species.
Molecular sieves are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three letter code and are described in the “Atlas of Zeolite Framework Types,” Sixth Revised Edition, Elsevier, 2007.
ERS-7 is a single crystalline phase zeolite having a structure consisting of 17-sided (46546582) “picnic basket”-shaped cages connected by 8-membered ring windows with 4.7×3.5 Å free dimensions. The framework structure of ERS-7 has been assigned the three-letter code ESV by the Structure Commission of the International Zeolite Association.
Italian Patent No. 1270630 discloses zeolite ERS-7 and its synthesis using an N,N-dimethylpiperidinium cation as a structure directing agent. ERS-7 is reported to have a SiO2/Al2O3 mole ratio between 15 and 30.
It has now been found that crystalline molecular sieves having ESV framework topology and having a SiO2/Al2O3 mole ratio of from 5 to 12 can be prepared using an N,N′-dimethyl-1,4-diazabicyclo[2.2.2]octane cation as a structure directing agent.